Lysosomal .beta.-mannosidase (EC 3.2.1.25) is an exoglycosidase that cleaves the single p-linked mannose residue from the non-reducing end of all N-linked glycoprotein oligosaccharides. The primary storage products associated with the enzyme deficiency are the trisaccharide Man.beta.1-4GIcNAc.beta.1-4GIcNAc and lesser amounts of the disaccharide Man.beta.1-4GIcNAc. Jones, M. Z. et al., J. Biol. Chem. 256:5181-5184 (1981 ) and Jones, M. Z. et al., J. Inherited Metab. Dis. 15:57-67 (1992). Deficiency of .beta.-mannosidase activity results in an autosomal recessive inherited disorder, .beta.-mannosidosis. This lysosomal storage disease was first described in Nubian goats (Hartley, W. J. et al., Acta Neuropathol. 25:325-333 (1973); Jones, M. Z. et al., J. Biol. Chem. 256:5181-5184 (1981); Healy, P. J. et al., Aust. Vet. J. 57:504-507 (1981) and Jones, M. Z. et al., J. Biol. Chem. 256:5185-5188 (1981)) and more recently has also been found in humans and cattle. Wenger, D. A. et al., N. Engl. J. Med. 315:1201-1205 (1986); Cooper, A. et al., N. Engl. J. Med. 315:1231 (1986); Dorland, L. et al., J. Inherited Metab. Dis. 11:255-258 (1988); Kleijer, W. J. et al., J. Inher. Metab. Dis. 13:867-872 (1990); Cooper, A. et al., J. Inherited Metab. Dis. 14:18-22 (1991); Poenaru, L. et al., Clin Genet 41:331-334 (1992); Wijburg, H. et al., Eur. J. Pediatr. 151:311 (1992) Levade, T. et al., Ann. Neurol. 35:116-119 (1994); Abbitt, B. et al., J. Am. Vet. Med. Assoc. 198:109-113 (1991); Bryan, L. et al., Biochem. Biophys. Res. Comm. 173:491-495 (1990) and Jolly, R. D. et al., N. Z. Vet. J. 38:102-105 (1990). Affected goats and cattle have very similar clinical features which include inability to stand, facial dysmorphism, intention tremors, and pastern joint hyperextension. Bryan, L. et al., Biochem. Biophys. Res. Comm. 173:491-495 (1990); Jolly, R. D. et al., N. Z. Vet. J. 38:102-105 (1990) and Jones, M. Z. et al., J. Inherited Metab. Dis. 7:80-85 (1984). Deafness is a consistent finding in affected goats but not in newborn calves. Widespread cytoplasmic vacuolation and dysmyelination in the central nervous system are characteristic lesions. Jones, M. Z., J. Neuropath. Exp. Neurol. 42:268-285 (1983) and Lovell, K. L. Acta Neuropathol. 62:121-126 (1983). Affected goats and calves are hypothyroid, possibly accounting for the CNS hypomyelination. Boyer, P. J. et al., Lab. Invest. 63:100-106 (1990) and Lovell, K. L. et al., J. Inherited Metab. Dis. 14:228-230 (1991). The affected ruminants display a profound deficiency of .beta.-mannosidase activity in plasma and various tissues. Jones, M. Z. et al., J. Biol. Chem. 256:5185-5188 (1981); Abbitt, B. et al., J. Am. Vet. Med. Assoc. 198:109-113 (1991) and Cavanagh, K., Am J. Vet. Res. 43:1058-1059 (1982). Affected animals usually die in the neonatal period if intensive care is not provided.
In contrast with the ruminant .beta.-mannosidosis, the human cases have a milder clinical expression and exhibit considerable heterogeneity. Wenger, D. A. et al., N. Engl. J. Med. 315:1201-1205 (1986); Cooper, A. et al., N. Engl. J. Med. 315:1231 (1986); Dorland, L. et al., J. Inherited Metab. Dis. 11:255-258 (1988); Kleijer, W. J. et al., J. Inher. Metab. Dis. 13:867-872 (1990); Cooper, A. et al., J. Inherited Metab. Dis. 14:18-22 (1991); Poenaru, L. et al., Clin. Genet. 41:331-334 (1992); Wijburg, H. et al., Eur. J. Pediatr. 151:311 (1992) and Levade, T. et al., Ann. Neurol. 35:116-119 (1994). Clinical expression ranges from mild peripheral neuropathy and depression (Levade, T. et al., Ann. Neurol. 35:116-119 (1994)) to dysmorphology, mental retardation and speech and hearing defects. Wenger, D. A. et al., N. Engl. J. Med. 315:1201-1205 (1986); Dorland, L. et al., J. Inherited Metab. Dis. 11:255-258 (1988) and Kleijer, W. J. et al., J. Inher. Metab. Dis. 13:867-872 (1990). In human .beta.-mannosidosis the major accumulated product is the disaccharide Man,81-4GIcNAc. Van Pelt, J. et al., Clin. Chim. Acta 187:55-60 (1990) and Cooper, A. et al., J. InheritedMetab. Dis. 11:17-29 (1988). Presumably the variability and severity of the mutations responsible for inactivation of .beta.-mannosidase account for some of the phenotypic variation in the human cases. The differences in disease expression between ruminants and humans may be related to the types of mutations, species differences in development, the nature of the storage products and/or the effects on thyroid function.
Bovine .beta.-mannosidosis has recently become a significant problem in the bovine Saler breed and in cattle cross-bred with the Saler breed. It is estimated that the number of animals at risk in North Amedca is approximately 70,000 pure-bred and 350,000-750,000 mixed-breed cattle and the carrier rate is predicted to be 20%-40%. Because .beta.-mannosidosis is an autosomal recessive disease, carriers have one normal copy and one mutant copy of the .beta.-mannosidase gene and although they may produce diseased offspring when bred with other carriers, they do not show any symptoms of the disease.
Presently, in order to determine whether a carrier has .beta.-mannosidosis, the .beta.-mannosidase enzyme activity in blood plasma or leucocytes is measured. Unfortunately this method is not very accurate because the range for the level of the enzyme in carriers overlaps with the normal range. In addition, in animals, the method is further complicated by seasonal variation of .beta.-mannosidase levels. Moreover, the enzyme assay test cannot be used to determine carrier status in mixed-breed cattle due to species variation in enzymatic activity.
It would thus be desirable to provide the nucleotide sequence of the gene coding for .beta.-mannosidase. It would also be desirable to provide the mutation in the nucleotide sequence of the gene coding for .beta.-mannosidase that causes .beta.-mannosidosis. It would further be desirable to provide the amino acid sequence of .beta.-mannosidase. It would also be desirable to provide oligonucleotide probes for detecting the .beta.-mannosidase nucleotide sequence and mutations therein. It would further be desirable to provide a method for detecting .beta.-mannosidosis in a ruminant and more specifically, in a bovine. It would also be desirable to provide a method for screening for a carrier of an abnormal .beta.-mannosidase gene. It would further be desirable to provide a diagnostic assay kit for detecting .beta.-mannosidosis.